System for correcting sound records



Aug. 13, 1935. R. J. POMEROY 2,010,959

. SYSTEM FOR CORRECTING SOUND RECORDS Original F iled May 22, 1928 2 Sheets-Sheet l 20V JZ/ 6 z -lz/ z 2 J4 I 65 2 26 Inventor H 60 JZqyJ Pamerqy.

- Aug. 13, 1935. R. J. POMEROY 2,010,959

M 'FoR ND RECORDS Patented Aug. 13, 1935- UNITED STATES PATENT o rIcE Radio Corporation of America, a

of Delaware corporation Griginal application May 22, 1928, Serial No.

279,790, new Patent No. 1,828,941, dated'october f 27, 1931. Divided and this application Septemher 28, 1931, Serial No. 565,571. Renewed September 15, 1933 9 Claims. (01. 179-4003) This invention relates generally to sound recordation and reproduction; and it may be stated as a general object of ,theinvention to provide methods and means for compensating'the distortions which arise in the recordation and reproduction of sound. This case is a companion to my application entitled System for correcting sound records, Ser. No. 279,789, filed May 22,

, 1928, Patent No. 1,828,940, issued Oct. 27, 1931,

, and volume.

and is directed to the general subject matter therein set forth. The present invention is within the scope of thebroader claims included within said prior application. The present applica tion is a division of my application entitled System for correcting sound records, Ser. No. 279,790, filed May 22, 1928, Patent No. 1,828,941, Oct. 27, 1931, and comprises subject matter and claims divided from said original application.

The invention is broadly applicable to any record of sound waves, but is probablymos't conveniently illustrated and described in connection with the photographic type of record; The particular type of photographic record with'which I have chosen to illustrate the invention consists of shaded band of constant density, a Wavy or variable outline representing the sound character It is to be understood, however, that no limitation to that type of record is in tended by such illustration. I

In recording and reproducing sound, distortions are always introduced by'reaso-n of nonlinear characteristics of the-various units involved. In photographic recording, it is often true that the chief distortions areintroduced in the reproducing systems, and particularly by the speaking unit, the distortions of the recording system being relatively small bycomparison, and

the chief concern is therefore with the distorby what may be termed a photographic method,

in which an original photographic recordis made, and then reproduced as sound. The distorted sound thus obtained is photographically recorded, and a negative of the original record to make a correction record, and this correction record is finally photographically combined side by side with an original record to'm'ake the distortion correctedrecord. In Patent No. 1,828,941, of which the'present application is a division, there is described a method which substitutes for the photographic combining of the original and distortion records, the combining of electrical sound currents representing the distortion and original records, whereby a resultant electrical current is obtained representing the differences of said record, or in other words the distortion alone. A

record 'of this distortion current is then made upon a film and then subsequently printed side by side along with an original record, orthe distortion representing record may be made directly upon a film containing the original record. In either case, the result is 'a distortion corrected record, or in other words an original record to which the distortion has been relatively added in areverse sense, so that the distorting effects of the units involved in reproducing the record will result in the sound finally reproduced having the -original undistorted wave form.

The :method specifically claimed in applica" tion Ser. No. 279,790 involves the making of an original record, the reproduction and recording of sound from a sound current corresponding to that used in making said original record, whereby there is obtained both an original record and a record involving the distortions of reproducing and recording sound, then producing'sound currents from each of said records simultaneously and combining'said currents differentially so that a current representing the distortion only is obtained, recording that distortion representing current, and finally combining the record so obtained with an original record. The specific Variation claimedwithin the present application involves a'simplification in that no actual record of the sound as distorted in the reproducing and Fig. 1 is a diagrammatic layout of a system for" making the original sound record and the distortion representing or correcting record;

Fig. 2 shows an original negative photographic record; l l

' Fig. 3 is a diagram of the electrical current used to make the original; record;

Fig. l is a diagram of the electrical current distorted by the system;

Fig. 5 shows the current obtained by differentially combining the currents of Figs. 3 and 4;

Fig. 6 shows a photographic distortion-correction record made by recording the current of Fig. 5; r

Fig. 7 shows a photographic distortion correcte record; and,

Fig. 8 shows a variational system for making A second plate having a slit S2 is shown positioned opposite the glow tube, and beyondit is a photoelectric cell P1. Leads l5, it from the photoelectric cell P1 connect to an amplifier A2, and the output leads'22, 23 of amplifier A2 connect to a speaker H. Microphone M1 picks up the original sound, and an electrical sound current is conducted therefrom by leads l8, ii to amplifier A1, and thence, in amplified state, is conducted by leads i2, it to glow tube G1, the traveling film M being light affected by the glow tube to take a negative sound record No oi the original undistorted sound. A negative photographic record, in the terminology herein employed, is the original photographic record employed in obtaining sound. A

positive record is a reversal of this negative, or in other words is the record which would be obtained by ordinary light printing from a negative record. The record No actually contains distortions introduced within the recording system, but these are capable of being reduced to comparatively negligible proportions, and the distortions of recording may therefore be disregarded for the instant purpose, it being later shown, however, that the recording distortions are also compensated by the system. Light rays are also transmitted from glow tube G1 through slit S2 and affect the photoelectric cell P1, and resulting sound current from the photoelectric cell is conducted by leads I5, 96 to amplifier A2, the amplifier current passing to speaker H and there being reproduced as sound.

Sound'reproduced by speaker H is picked up by microphone M2, a sound current being conducted therefrom to an amplifier A3. The output leads 20 and 2t of amplifier A3 then carry an electrical current which is identical with that in the output circuit l2, E3 of amplifier A1 except for having imposed thereon the distortions arising in. the reproducing system P1, A2, and H, and the recording system M2 and A3. The reproducing system P1, A2, H must be one having characteristics identical with the one to be used in final reproduction, and the recording system M2, A3, is one having characteristics identical with .the original recording system M1, A1, or one introducing little or no distortion. The electrical currents in circuits i2, i3 and 2t, iii are now to be differentially combined, and for this purpose connections such as leads BB and Si may be made between said circuits. Circuits it, IS and 2t, 2t are connected with such regard for polarity that their currents oppose one another, the resultant current then. representing their difierence, or in other words the distortion alone. Potentiometers t6 and are shown connected in the circuit for the purpose of so balancing the potentials that the current components can exactly neutralize, leaving simply the difierential distortion current. In balancing the circuit, I may proceed as follows: For the system of Fig. 1 there may be at least one frequency of sound curr nt at which there will be substantially no distortion. This frequency being ascertained, it

is induced in the system, and the system is then balanced, as by potentiometers wi l, and 55, until no resultant current fiows in circuit Elli, 6 i

In series with circuit at, ti are leads that connecting to an amplifier A4. The output of amplifier A4 is led to a glow tube G2, before which runs a film till, a usual light slit being shown be tween the glow tube and film at 5i. This film 50 takes a record 52 of the amplifier distortion representing current.

In Fig. 2 is shown the film illwith the original sound record No having a variable outline the record being shown greatly enlarged for the purpose of exhibiting more clearly the relations between the several records utilized in the system. Fig. 3 shows the original electrical current wave 30 in circuit i2, it, which current was used in making original record No. Fig. l shows the distorted current wave iii in circuit 2i, wave ti being like wave 3% except for the distortions of glow tube G1, reproducing system Pl, A2, H and system M2, A3, which last matches system "i /Z1, A1. It will be understood that while the current wave Si is obtained directly from the sound current in circuit l2, it, current wave 35 is the same, in efiect, as would be obtained by reproduction oi record No. Distorted current wave 35 is shown superposed in dotted lines upon original current wave 33 in Fig. 3, and it will be observed that the distortion introduced by the system is represented by the difierence between curves and 3%. Whether the amplitude of the distorted wave 32 is greater or less than that-cl original wave SE3 depends upon the resultant total of the individual characteristics of the several units involved, and

in any specific case may depend upon the varying factors of sound character, such for instance as sound frequency. In other words, the amplitude distortion may be either plus or minus with respect to the original current, and although only the r plus case is here illustrated it will become apparent that the system corrects the distortions in either case.

Fig. 5 shows the distortion representing cur- 'rent wave B l obtained when the currents of circuits l2, l3 and 28, 25 (Figs. 3 and 4) are differentially combined in circuit 68, (it, this resultant current wave representing the difference of said currents when oppositely combined. Thus, with the system in balance, the current in circuit 68, 65, may be an alternating current representing the difference of the currents in circuits 5?, it and 2t, 2! the direct current sound representing components being entirely neutralized, while the output of amplifier A consists of a direct current with an amplification oi the distortion representing current wave 3 impressed upon it.

Fig. 6 shows the film 5t having a distortion representing record C, made by recording the current output wave of amplifier A4, said record a depression in the final outputcurrent wave (of.

record C of the negative correction record-C ob-' tained as just-described, andiwith an [original negative No along the other, asshown in Fig. .7, care being taken that'the two prints, the original record and the correctionrecord, are accurately registered with each other.

In case the'polarity of amplifier A4 isreversed with respect to circuit 60, 6|, the positive cor- 7i rection record C maybe obtained-directly, and

may be printed directly with the original record No. as in Fig. 8. The system shown in Fig.8. is generally similar to that shown in Fig. 1., but may be considered as having its input leads to am- 1 plifier Ar'reversed fromthe arrangement ofFig.

1, so that the correction recordobtained will be positive C rather than the negative C; Inthe case illustrated, the correction record C is made directly upon the film l 4 which takes the original negative No, so that the final film illustrated in Fig. 7 is obtained in one step. In either case, whether the'record of Fig. 7 has been made by the system of Fig. 1 and subsequent printing operations, or. directly by the systern of Fig. 8, there has then been added to the original record No a correction band ofopacity C" which varies in width .by the amountof the distortions and in a direction or sense negative to that of the distortions. 'Another manner of expressing this relation is that there has been added to the original record a compensating band of opacity which varies by the amount of but reversely to the distortions of the system.

- The result of running the distortion corrected film 53 through the reproducing system is .then

,2 pensating solely for the disabilities of reproducs tion; but the system actually compensates for the relatively small disabilities of recording as well, as will now be explained. Starting at the microphone M1 in Fig. 1, the sound wave representation, after passing through amplifier A1 and being transformed from a modulated electric current to modulated light waves, has become distorted by the elements of the recording system, and the original sound record No therefore contains those recording distortions. The sound current picked up by the photoelectric cell P1, which current also has those recording distortions, is passed through the amplifier A2, and, with the additional distortions of reproduction, is reproduced as sound. The distortedsound is then picked up by microphone M2 and the resulting current passed through amplifier A3 therefore contains the distortions of original recording, plus the distortions of reproduction, plus the distortions of microphone M2 and'amplifie'r As, which last. correspond to the recording distortions of M1 and. A1 and hence may be referred to as recording distortions- It will be observed that therecording distortions are added twice. The current in circuit l2, l3, it'will be remembered,

contains the; distortions of the original recording elements M1 and A1, so that the current obtained by differentially combining the output of am-' plifier A3 with the current in. circuit 1 2, I3, is then the difference of said two currents, and comprises only thedistortions ofrecording'plus the distortions of reproduction. The record C is therefore a recordof the distortions of recording plus the distortions of reproduction. The original record No,-WhiCh contains the distortions of recording, is then compensated by the addition of correction band. C both for its distortions of recording and also for the distortions of its reproduction. Both the recording and reproducing systems utilized to modify the records must, of course, be the same, or have identical characteristics, as the ones used originally in recording and in finally reproducing the sound.

The system as now described is capable of considerable modification and rearrangement by varying printing operations, and by substituting positives for negatives, and vice versa, in various parts of the system; and the electrical system is also capable of considerable modification, all within thescope of the invention. Therefore I wish it to be understood thatthe invention is not to be limited except as may be construed by a fair interpretation of the appended claims.

Lolafim: V 1, The method of correcting sound records that includes, producing an electricalsound current from the original sound, simultaneously making an original sound record from the sound current,

and audibly reproducing sound from the sound current, such sound having the distortions of reproduction, producing an electrical sound current from the distorted sound, differentially combining said last mentioned sound current with the first mentioned sound current in such a manner that the sound currents are neutralized except for a distortion-representing current, making a correction record of the distortion-representing current, and making a distortion-corrected record by modifying the original record by the correction record in such a manner as to add the distortions reversely to the original record.

2. The method of correcting sound records that includes, producing an electrical sound current.

from the original sound, simultaneously making an original sound record from the sound current, and audibly reproducing sound from the sound current, such soundhaving the distortions of reproduction, producing an electrical sound current from the distorted sound, differentially combining said last mentioned sound current with the first mentioned sound current in such a manner that the sound currents are neutralized except for a distortion-representing current, and placing a record of the distortion-representing current in such association with the original record as to add the distortions reversely to the original record.

3. The method of correcting sound records that includes producing an electrical sound current from the original sound, simultaneously making an-original photographic sound record from the sound current, and audibly reproducing sound from the sound current, such sound having the distortions of reproduction, producing an electrical sound current from the distorted sound, differentially combining said last mentioned sound ourthat the currents are neutralized except fora distortion-representing current, making a photographic correction recordof the distortion-representing current, and making'a photographic distortion-corrected record by modifying the origrecord by the correction record in such a manner as to distort said original record reversely to the distortions introduced in reproduction.

l. The method of correcting sound records that includes, producing a sound current from the original sound, simultaneously making an original photographic sound record from the sound'current, and audibly reproducing sound from the sound current, such sound having the distortions of reproduction, producing a distorted sound current from the distorted sound, differentially combining said distorted sound current with the first mentioned sound current in such a manner that the currents are neutralized except for a distortion-representing current, making a photographic correction record negative of the distortion-representing current, making a photographic distortio-n corrected record by printing a film with an original record and with a positive of the correction record, all in such a manner that the distortions are added rcversely to the original record.

5. The method of correcting sound records that includes, producing an original sound current from the original sound, making an original photographic sound record from the original sound current, audib-ly reproducing sound corresponding to the said original sound current, such sound having the distortions of reproduction, producing a distorted'sound current from the distorted sound, differentially combining said distorted sound current with a portion of the original sound current in such amanner that said currents are neutralized except for a distortion-representing current, making a photographic correction record negative of the distortion-representing current, and making a photographic distortion-corrected record by print-inga film with an original record and-with a positive of the correction record, all insuch a manner that the distortions are added reversely to the original record.

6. The method of correcting sound records that includes, producingan original sound current from the original "sound, making an original photographic sound record from the original sound current, audibly reproducing sound corresponding to said original sound current, such sound having the distortions of reproduction, producing a distorted sound from the distorted sound, differentially combining said distorted sound current with a portion of the original sound current in such a manner that said cur-' rent with the first mentioned in such a manner.

rents are neutralized except for a distortion-representing current, making a photographic correction record of the distortion-representing current and modifying said original record by the correction record in such a manner as to add the distortions reversely to the original record.

7. The method of correcting sound records that includes, producing an original sound current from the original sound, making an original sound record from said sound current, audibly reproducing sound from said sound current, such sound having distortions of reproduction, producing a distorted sound current from the distorted sound, differentially combining said distorted sound current with a sound current representing the original sound, in such a manner that the sound currents are neutralized except for a distortion-reps resenting current, making a correction record of said distortion-representing current, and making a distortion corrected record by modifying the original record by the correction record in such a manner as to add the distortions reversely to said originalrecord.

' 8. The method of correcting sound records that includes, producing an original sound current from the original sound, making an original sound record from said sound current, audib-ly reproducing sound from said sound current, such sound having distortions of reproduction, producing a distorted sound current from the distorted sound, differentially combining said distorted sound current with a portion of the sound current used in making said original record, in such a manner that the sound currents are neutralized except for a distortion-representing current, making a correction record of the distortion-representing current, and making a distortion corrected record by modifying the originalreccrd by the correction record in such a manner as to add the distortions reversely to said original record.

9. In a system for correcting sound records, means for producing an original electrical sound -cur ent from the original sound, photographic ROY J. POMEROY. 

